Process for the production of vegetable protein fibers



Dec. 16, 1958 T c. LIS 2, 63

PROCESS FOR THE PRODUCTION OF VEGETABLE PROTEIN FIBERS F iled Nov. 1,1954 STRETCH POSTCURE DRY POSTCURE SOLUTION PRECURE FILTER SPIN 8:

COAGULATE IN VENTOL ZE'N M mmflm SOLUTION FILTER DEAREATE ATTORNEYPRUCESS FOR THE PRODUCTION OF VEGETABLE PROTEIN FIBERS Leon C. Lis,Narragansett, R. I., assignor to Virginia- Carolina Chemical orporation,Richmond, Va., a corporation of Virginia Appiication November 1, 1954,Serial No. 465,921

4 Claims. (Cl. 1854) This application is a continuation-in-part of myapplication Serial No. 228,116 filed May 24, 1951 and now abandoned.

This invention relates to the production of synthetic textile fiberfro-m corn proteins known as zein.

Objects of my invention are to provide a process which will producefiber of high quality with respect to the properties generallyconsidered in evaluating fiber such as uniformity, wet and dry tensilestrengths and elongations, shrinkage, dyeing properties, retention ofstrength after dyeing, freedom from adhering fibers etc. and whichpresents no particular obstacle to its commercial operation such as highcost of materials, plant, labor etc.

A more particular object of my invention is to provide an improvedprocess with respect to the cur-ing of the fiber by the action offormaldehyde.

The essence of the invention is believed to reside in the use of a highhumidity atmosphere i. e. an atmosphere which is substantially saturatedwith water vapor in the curing treatment of the fiber.

The fiber may be formed by any known and suitable method, for instance,by extruding an alkaline solution of zein, which may containformaldehyde as disclosed in U. S. Patent No. 2,478,248 e. g. a solutioncontaining from about 16% to about 22% of zein and from 0.5 to offormaldehyde based on the weight of the zein in an aqueous solution ofsodium hydroxide, said zein solution having a pH value of about 11 to12.5, into a suitable coagulating bath, e. g. a bath containing fromabout 1% to about 3% of sulfuric acid, from about 2% to about 10% offormaldehyde, from about 1% to about 6% of ammonium sulfate and fromabout 0.1 to 0.5% of goulac, at a temperature of from about 80 F. toabout 100 F. The coagulated fibers are collected together into the formof a tow as they are withdrawn from the coagulating bath and areprecured by being permitted to remain wet with the adhering coagulatingbath for a suitable length of time, c. g. from about /2 to about 3hours. This may be done by passing the tow through a closed chamber theatmosphere of which is maintained at a high humidity and at atemperature of from about 80 F. to about 100 F. by the introduction ofsteam as required.

The tow of fibers then passes to the stretching operation. In thestretching operation the tow is passed back and forth between twoconical or stepped rollers, progressing to larger and larger diameterwhereby it is stretched the desired amount e. g. from 50% to 300% ormore.

The two rollers dip into a body of liquid such as water maintained atfrom about 85 F. to about 140 F. so that as the tow passes back andforth over the rollers its temperature is raised to the desiredstretching temperaturei The tow, as it leaves the stretching rollers iskept under tension and this tension is maintained while the tow isimpregnated with postcure solution by passing back and forth around twocylindrical rollers dipping into the postcure solution. The postcuresolution, at a temperature of from about 110 F. to about 140 F.preferably is a substantates Patent 2,864,663 Patented Dec. 16, 1958squeezed to remove solution which otherwise would drain away thusleaving the tow wet with about its own dry weight of postcure solution.At this point the tension on the tow is relaxed and the relaxed tow isdelivered to the postcure chamber. In the postcure chamber the tow isheld at a temperature below 212 F. and preferably at about 1l0140 F. fora-corresponding period of time depending upon the degree of postcuringdesired, i. e. the

type of fiber product to be produced. The period generally falls withinthe range from 30 minutes to 2 hours. This treatment may be carried outby plaiting the tow on a belt which moves slowly through a chamber inwhich the selected postcure temperature is maintained for example by theintroduction of steam. The atmosphere in the postcure chamber ismaintained at a relatively high humidity, e. g. at least relativehumidity.

The process to this point is described in the accompanying flow-sheet.

The tow is then washed to varying degrees depending upon the qualitiesdesired in the finished product and it may also be subjected to a bakingtreatment. In general the tow, following the postcure treatment, may bemerely surface washed, i. e. washed for about 2 minutes with cold waterto remove adhering postcure solution and then dried and baked or it maybe subjected to ,a thorough washing treatment with warm water e. g. atabout 80 F. for about 30 minutes to remove not only adhering'postcuresolution but also to wash solution out of the fiber structure afterwhich it is dried e. g. at about 150 F. for about 60 minutes and thenbaked or merely dried. The after treatment of the fiber, i. e. crimping,cutting into staple, the application of various finishing materials,etc. form no part of my present invention and therefore need not beconsidered.

The baking treatment is applied to the dried fiber tow and may be variedas to both time and temperature depending upon the specific propertiesdesired but generally is carried out at a temperature of about 300 F.Depending upon the size of the tow it is necesary to adjust the bakingtime so that all portions of the fiber will be subjected to the selectedbaking temperature for at least about 15 minutes.

The fiber after baking and particularly if the washing after thepostcure and before drying was limited to a mere surface washingpreferably is given a final washing to remove any chemicals left in oron the fiber.

As has been indicated in the foregoing description the conditionsemployed in the several steps of the process.

are capable of considerable variation. For instance, the spin solutionmay vary as to both composition and temperature, the coagulating bathalso may vary as to composition and temperature and the precureoperation may be varied or even omitted, the object of these steps beingprimarily to deliver a coagulated fiber to the stretching and postcuringsteps. Many specific methods'are known for accomplishing this result.

The feature of my process which contributes most to the control of theproperties of the fiber product, to plant capacity and to the productionof a tow with the fibers thereof well-alined is the so-called drypostcure step described above in which the tow carrying from about 70%to about of its weight of postcure solution is plaited onto a beltconveyor and transported through a chamber the atmosphere of which ismaintained highly humid and at the desired temperature, for instance bythe introduction of steam. It is possible, of course to vary thecomposition of the postcure solution and particularly the formaldehydecontent thereof and it is possible also to vary the temperature in thepostcure chamber but generally the desired variation in the qualities ofthe fiber may be obtained by simply varying the time that the tow isheld in the postcure chamber.

The washing, drying andbaking steps which follow the postcure havebeensufliciently described above.

Extensive research work has been done in connection with the productionof protein fiber. Theories have been advanced to explain the purpose andeffect of the different ingredients of the coagulating, precure andpostcure solutions. My invention is not concerned with these mattersbutonly with the provision of a simple and efficient method or procedurefor handling the fiber as it isbeing subjected to the known sequenceofcoagulating, precuring, stretching, postcuring, washing, drying andbaking steps; My invention'is more particularly concerned withthestretching, saturatingand postcuring steps and especially'with theso-called dry postcuring' stepin which the fiber-is cured by being heldin or passed through a warm, or hot, humid atmosphere while at rest on aconveyor, where the curing is effected by the adhering and absorbedcuring solution as distinguished from prior methods in which thepostcuring generally has been effected by holding the tow for therequired time in a postcuring bath maintained at the requiredtemperature.

The invention is illustrated by the following specific examples.

EXAMPLE 1 An aqueous zein solution containing 20% by weight of zein and2% by weight of sodium hydroxideand having a pH value of 12.5 was spuninto an aqueous coagulating bath containing 1.5% by \veightof sulfuricacid, 4.4%

by weight of formaldehyde, 2.5% by weight of ammo-' bath solutionthrough a closed chamber maintained at a temperature of 88 F. and at arelative humidity of 100%, each portion of the tow being subjected tothe atmosphere in said chamber for 60 minutes. The tow was then passedback and forth between two stepped stretching rollers which dipped intoa water bath maintained at 130 F. and thereby washed free of adheringcoagulating bathsolution and stretched 295%. The tow was then passed,while being maintained under sufficient tension to maintain the stretch,back and forth between two rollers dipping into an aqueous postcuresolution containing 3.5% by weight of formaldehyde, 5.0% by weight ofsulfuric acid and sodium chloride to 100% saturation. The tow was thensqueezed gently between rollers to remove excess postcure solution andleavean amount of said solution in the tow about equal to the dry weightof the tow. The tension on the tow was then relieved and the tow waspassed through a chamber maintained at 120 F. at a relative humidity of100%, each portion of the tow being subjected to the atmosphere in saidchamber for 2 hours. The tow was then washed in water at 80 F. for 27minutes and then dried at 150 F. for 60 minutes and then baked at 300 F.for 60 minutes.

The resulting fiber had the following properties:

Cond. elongation 43 percent.

4 EXAMPLE 2 Sample 1 Sample 2 2hrs. at120 F. 100% Soft and open.

2 hrs. at 81 F.

Slightly adhered filaments.

Difference of Curo Rel. Humidity of Cure Appearance of Sample-Mechanical Properties:

Denier of filament Wet tensile, gm./den Wet elongation, percent. 00nd.Tensile, gin/den Cond. Elongatiion, Percent: Shrinkage in Acid Dyeing,Percent. Dye Exhaust, Percent.. Properties after Acid Dyeing:

Wet Tensile, gmJden Wet Elongation, Percent- Cond. Tensile, gmJden.--Cond. Elongation, Percent It is to be noted that the effect of thispostcuring method i. e. subjecting the fiber to an atmosphere at 110-140 F. at a relative humidity of at least for from 30 minutes to 2hours, gives a greater effect on fiber produced as described in Example1 than on fiber produced by theprocess of U. S. Patent No. 2,478,248 asdescribed in Example 2 but the effect in both cases is significant andWell worthwhile.

I'claim:

1. In a process of curing synthetic zein fiber with formaldehyde thestep which consists in stretching the fiber, impregnating the fiber instretched condition with about an equal weight of an aqueous solutioncontaining from about 3% to about 10% of sulfuric acid, from about-3% toabout 10% of formaldehyde and at least 90% saturated with sodiumchloride, relaxing the fiber and subjecting it to an atmosphere which isat least 90% saturated with water vapor at a temperature within therange from about F. to about 140 F. for a period of from about 30minutes to about 2 hours.

2. Process as defined in claim 1 in which the aqueous solution containsabout 3.5% of formaldehyde and 5% of sulfuric acid and in which thetemperature is maintained at F. for 2 .hours.

3. Process for the production of synthetic textile fiber which comprisesextruding an aqueous zein solution containing from about 0.5 to about10% of formaldehyde into an aqueous bath containing from about 2 toabout 10% of formaldehyde, and holding the resulting fiber in contactwith said solution in an atmosphere which is saturated with water vaporat a temperature within the range from about 80 F. to about 100 F. for aperiod of from about /2 hour to about 3 hours, and thereafter treatingthe fiber as defined in claim 1.

4. In a process for the production of zein fiber involving the steps ofspinning an alkaline zein solution into an acid coagulating bath,stretchingsthe fiber and curing the fiber by treatment withformaldehyde, the improvement which consists in impregnating a tow ofthe fiber in the stretched condition with an aqueous solution containingfrom about 3% to about 10% of formaldehyde, from about 3% toabout 10% ofsulfuric acid and at least 90% saturated with sodium chloride, relaxingthe fiber tow and subjecting. the relaxed to-w containing about an equalweight of said solution to an atmosphere which is main- References Citedin the file of this patent UNITED STATES PATENTS Swallen May 2, 1939 6Wormell July 21, 1942 Atwood Feb. 29, 1944 Cline Oct. 15, 1946 CrostonAug. 9, 1949 Tetlow Aug. 28, 1951

1. IN A PROCESS OF CURING SYNTHETIC ZEIN FIBER WITH FORMALDEHYDE THESTEP WHICH CONSISTS IN STRETCHING THE FIBER, IMPREGNATING THE FIBER INSTRETCHED CONDITION WITH ABOUT AN EQUAL WEIGHT OF AN AQUEOUS SOLUTIONCONTAINING FROM ABOUT 3% TO ABOUT 10% OF SULFURIC ACID, FROM ABOUT 3% TOABOUT 10% OF FORMALDEHYDE AND AT LEAST 90% SATURATED WITH SODIUMCHLORIDE, RELAXING THE FIBER AND SUBJECTING IT TO AN ATMOSPHERE WHICH ISAT LEAST 90% SATURATED WITH WATER VAPOR AT A TEMPERATURE WITHIN THERANGE FROM ABOUT 110*F. TO ABOUT 140*F. FOR A PERIOD OF FROM ABOUT 30MINUTES TO ABOUT 2 HOURS.